[45, 68–72]. Another type of all-fiber polarizer is based on longer lengths
of single-polarization fibers often wrapped in small-diameter coils to induce
differential polarization bending loss [73].
When a proper birefringent crystal is used to replace the portion of removed
cladding, the refractive index of the crystal is less than that of the effective index of
the waveguide for the transmitted mode and greater than that of the orthogonal
mode, causing the unwanted light to escape into the bulk crystal. Birefringent
properties of liquid crystals have been used to make an all-fiber polarizer in this
manner [74]. A similar approach, but without the birefringent material, uses a thin
multimode planar dielectric overlay of zinc sulfide, vacuum deposited ...